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List:       git-commits-head
Subject:    ARM: fix missing syscall trace exit
From:       "Linux Kernel Mailing List" <linux-kernel () vger ! kernel ! org>
Date:       2015-05-31 19:50:59
Message-ID: 20150531195059.6D59F66041C () gitolite ! kernel ! org
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Gitweb:     http://git.kernel.org/linus/;a=commit;h=1b97937246d8b97c0760d16d8992c7937bdf5e6a
Commit:     1b97937246d8b97c0760d16d8992c7937bdf5e6a
Parent:     965278dcb8ab0b1f666cc47937933c4be4aea48d
Refname:    refs/heads/master
Author:     Russell King <rmk+kernel@arm.linux.org.uk>
AuthorDate: Fri May 15 11:02:23 2015 +0100
Committer:  Russell King <rmk+kernel@arm.linux.org.uk>
CommitDate: Fri May 15 11:06:35 2015 +0100

    ARM: fix missing syscall trace exit
    
    Josh Stone reports:
    
      I've discovered a case where both arm and arm64 will miss a ptrace
      syscall-exit that they should report.  If the syscall is entered
      without TIF_SYSCALL_TRACE set, then it goes on the fast path.  It's
      then possible to have TIF_SYSCALL_TRACE added in the middle of the
      syscall, but ret_fast_syscall doesn't check this flag again.
    
    Fix this by always checking for a syscall trace in the fast exit path.
    
    Reported-by: Josh Stone <jistone@redhat.com>
    Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 arch/arm/kernel/entry-common.S | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index f8ccc21..4e7f40c 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -33,7 +33,9 @@ ret_fast_syscall:
  UNWIND(.fnstart	)
  UNWIND(.cantunwind	)
 	disable_irq				@ disable interrupts
-	ldr	r1, [tsk, #TI_FLAGS]
+	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
+	tst	r1, #_TIF_SYSCALL_WORK
+	bne	__sys_trace_return
 	tst	r1, #_TIF_WORK_MASK
 	bne	fast_work_pending
 	asm_trace_hardirqs_on
--
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